1. Field of the Invention
The present invention relates to a transmission assembly, and more particularly to a transmission assembly for converting rotating motion into linear motion, and the transmission assembly is provided with a chain for holding rolling elements.
2. Description of the Prior Art
To ensure that a transmission member moves at a high speed with low noise and to extend the service life of the transmission member, the transmission member is normally provided with a chain for holding rolling elements. The chain can prevent the rolling elements from impacting each other and prevent the occurrence of deviation of the rolling elements when the rolling elements move to the return path of the transmission member, thus ensuring smooth circulation while extending the service life of the transmission member.
For example, U.S. Pat. Nos. 6,089,117 and 6,286,383 disclose a transmission member which is provided with a chain. U.S. Pat. No. 6,089,117 discloses a guiding member which is provided at each end thereof with a guiding section for guiding the motion of a chain, but doesn't describe the operation of the chain within the load area (which refers to the area between the nut and the screw). Furthermore, U.S. Pat. No. 6,286,383 discloses that a threaded member is additionally engaged in the interior of the nut to guide the motion of the chain within the load area. However, none of them explain the operation of the chain within the load area. The chain of U.S. Pat. No. 6,286,383 essentially comprises the spacers 72 disposed at both sides of the rolling elements 73 and the link 71 for linking the spacers 72. Within the load area, the link 71 is located between the outer surface 52 of the screw 5 and the inner surface 62 of the nut 6. If the thickness T of the link 71 is not precisely designed with respect to the size of the screw 5 and the nut 6, the link 71 will be likely to interfere with the outer surface 52 of the screw 5 in such a manner that the link 71 presses against the outer surface 52 of the screw 5, causing friction, which will further cause distortion of the link 71. Therefore, the rolling elements 73 will be unable to abut closely against the spacers 72, as a result, stress is only applied to a single edge of the spacers 72 and accelerates the abrasion of this edge, reducing the service life of the chain. Further, it will also cause unsmooth motion of the chain or even the break of the link.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages.